The present invention relates to a rotary actuator with a cushion mechanism which can stop a normally and inversely swinging and rotating rotor at a rotational terminal end position in a cushioning manner.
As one of a rotary actuator generating a rotational force due to an air pressure, there is a vane type actuator. This is structured such that a rotatable rotor is provided in a center portion of a circular cylinder hole formed within a casing, a vane is mounted to the rotor, and the vane is swung and rotated in a normal and reverse direction due to an effect of air pressure, whereby a rotational force thereof is output via the rotor.
The vane type rotary actuator of this kind is generally structured such that the vane is brought into contact with a stopper so as to be stopped at a rotational terminal end position. Accordingly, since the rotor can not stop at the rotational terminal end position in a cushioning manner while the speed thereof is gradually reduced, there are disadvantages that an impact sound is generated at a time of stopping, a deterioration due to abrasion is easily facilitated in the collided portion and the like. Therefore, it is desirable to provide a vane type rotary actuator which can stop the rotor at the rotational terminal end in a cushioning manner.
A main object of the present invention is to provide a rotary actuator of a vane type provided with an air pressure type cushion mechanism.
Another object of the present invention is to provide a vane type rotary actuator having a compact and rational design structure in which a cushion mechanism is assembled within a casing in a compact manner.
In order to achieve the objects mentioned above, in accordance with the present invention, there is provided a rotary actuator having an air pressure type cushion mechanism for stopping a vane at least at one of normal and reverse rotational terminal end positions in a cushioning manner.
The cushion mechanism mentioned above has a first opening for discharging an exhaust air pressed out from a cylinder hole by a rotating vane to an external portion without limiting a flow amount, a second opening for discharging the exhaust air to the external portion in a state of limiting a flow amount and a flow amount adjusting mechanism for limiting a flow amount, the flow amount adjusting mechanism being connected to the second opening, wherein the first opening is provided at a position sealed by the vane before the vane of a hole surface in the cylinder hole reaches a rotational terminal end position, and the second opening is provided at a position which is not sealed by the vane after the vane reaches the rotational terminal end position.
In the rotary actuator in accordance with the present invention having the structure mentioned above, since the exhaust air is mainly discharged from the first opening freely when the vane is rotated, the vane rotates at a normal speed, however, since the first opening is sealed by the vane when the vane moves close to the rotational terminal end position, the exhaust air is discharged only from the second opening through the flow amount adjusting mechanism in a limited manner. Accordingly, an exhaust pressure is increased, and the vane reaches the rotational terminal end while the speed of the vane is reduced due to a back pressure generated by an increase of the exhaust pressure.
Therefore, in accordance with the present invention, it is possible to obtain a vane type rotary actuator provided with an air pressure type cushion mechanism. Further, since the cushion mechanism can be structured only by assembling a throttle hole, a check valve and the like in a casing and thereafter providing a through hole, a port and the like, it is possible to assemble the cushion mechanism within the casing in a compact manner, so that it is possible to obtain a vane type rotary actuator having a compact and rational design structure.
The actuator in accordance with the present invention may be provided with one vane or two vanes having the structure mentioned above. Further, the cushion mechanism may be set to two pairs of cushion mechanisms for stopping the vane at both normal and reverse rotational terminal end positions in a cushioning manner.
In the actuator provided with one vane, two packings are mounted to the vane. On the contrary, in the cushion mechanism, the first opening for discharging the exhaust air without limiting a flow amount is provided at a position sealed between the two packings before the vane reaches the rotational terminal end position, and the second opening for discharging the exhaust air in a state of limiting a flow amount is provided at a position which is not sealed by the packing even after the vane reaches the rotational terminal end position. Then, the first opening is connected to one supply port by the through hole within the casing and the second opening is connected to the same supply port via the flow amount adjusting mechanism.
Further, in the actuator provided with two vanes, the first vane functions for being driven by the air pressure and the second vane functions for operating the cushion. That is, two pressure chambers are formed in both sides of the first vane, the pressure chambers are respectively connected to the supply port, and the compressed air is alternately supplied to both pressure chambers from the supply port, whereby the first vane and the rotor are normally and inversely swung and rotated. Further, two cushion chambers are formed in both sides of the second vane, and one or both of the cushion chambers is directly connected to a breathing port through the first opening in the cushion mechanism and is connected to the breathing port via the second opening and the flow amount adjusting mechanism. Further, the first opening is provided at a position shut from the cushion chamber by the second vane before the second vane reaches the rotational terminal end position, and the second opening is provided at a position which is not sealed by the second vane even after the second vane reaches the rotational terminal end position. In the case that two sets of cushion mechanism having the structure mentioned above, it is desirable that these cushion mechanism commonly have one first opening and one breathing port, and the first opening is structured such as to be positioned at a center of swing area of the second vane.
In accordance with a particular embodiment, the flow amount adjusting mechanism is formed by a throttle hole, and a check valve which prevents the exhaust air discharged from the cylinder hole from flowing but allows a flow of a supplied air flowing into the cylinder hole from an external portion is provided in parallel to the throttle hole.
In accordance with another particular embodiment of the present invention, a valve chamber communicating with the second opening is formed in the casing and a hole member having the throttle hole is received within the valve chamber via a lip seal forming the check valve between the lip seal and a chamber wall, whereby the throttle hole and the check valve are assembled within the valve chamber.